The Q-hour (or "quantity" hour) meter to a considerable extent fulfills the need of utilities, and other electrical power suppliers and users for equipments and techniques to produce the maximum amount of information in return for a minimal possible investment of dollars, space and weight. In survey work, as well as in revenue billing, electrical quantities other than kilowatts and/or kilowatt-hours need to be determined. Quantities such as reactive power and energy, kilovolt-amperes and kilovolt-ampere-hours, power factors and other similar measurements, often are needed to provide the utility, customer, etc., with necessary information relative to an electrical system operation.
With conventional techniques for the measurement of reactive power and energy, two VARS-hour meters and two phase-shifting transformers would be required if both lagging and leading VARS need to be determined. In the majority of cases, one Q-hour meter without requiring the use of phase-shifting transformers, can fully meet this requirement, thereby resulting in substantial savings in material space and installation costs. With the availability of computers in industry today, the calculation of reactive power from two other measured quantities (watts and Q) poses no problem.
Watts may be expressed as EI cos .THETA.. When the proper voltages and currents are applied in a conventional motor-driven watt-hour meter, the torque produced on the meter is proportional to EI cos .THETA. defined as watts. The angle .THETA. is the power factor angle. In a similar fashion, reactive power is expressed as EI sin .THETA. or VARS. In as much as the watt-hour meter cannot directly recognize a sine function of an angle, a common method of measuring VARS (by means of a conventional motor-driven watt-hour meter) is to make use of a phase shifting transformer which displaces the voltage to the VAR-hour meter by ninety degrees. When the voltages to the meter for VAR measurement are displaced ninety degrees from the watt meter voltages, the conventional watt-hour meter then develops a torque proportional to EI cos (90.degree.-.THETA.) which may be shown to be equal to EI sin .THETA. or VARS. Voltages may be displaced either ninety degrees leading or ninety degrees lagging. Separate phase-shifting transformers and separate meters are required if both leading and lagging VARS are to be measured. It is this requirement that makes the Q-hour meter more desirable in both billing and survey recording systems.
A conventional Q-hour meter comprises a conventional motor-driven watt-hour meter in every detail. However, unlike the VAR-hour meter, a single Q-hour meter has the capability of measuring both leading and lagging VARS over some defined range of power factor. As noted above, a displacement of the watt-hour meter voltages by ninety degrees produces a value called VARS. By displacing the voltages any angle .THETA. (other than zero or ninety degrees), the torque on the motor driven watt-hour meter will not be proportional to watts or VARS, but will be proportional to a "quantity" called Q; thus a Q-hour meter. Conventional motor-driven Q-hour meters have been known to the industry for a period of time. It is a primary purpose of this invention to provide an elctronic solid state Q-hour meter which does not require the use of a third phase shifting potential transformer in order to meter Q hours.